Improvement in back centers for milling-machines



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AMos H. BRAIN-ARD,- or HYDE PARK, MASSACHUSETTS.

Leners raamt No. 110,951, and January 17, 1871.

|MPRovEMENT 1N eAcKcEm-Ens Fon MILLING-moulure.

The Schedule referred to in these Letters Patent and making part of the same.

.I, Amos H. BHAJNARD, of Hyde Park, in the county of Norfolk and State of Massachusetts, haveinvented a new and useful Improvement in Back Oen ters for Milling and other Machines, of which the following is a specification.

Nature and Object of thc Iiwcntion.

lhe'obj'ectof'ny invention is to' provide a simple Afig. l; 'and x /Figure 4 is a rear view of the bar a.

Similar lettersrefer to similar parts in all the Iigures. a is a bar of dovetaled section, made so as to slide easily in the block h, and held rmly by the gib s and set-screws c, iig. 3, as shown.

On the front end of the bar a is av male center, made in the usual manner, shown at c, iig. 2, which forms the support for the arbor or other work, while the opposite end is furnished witha forked knee, as shown at d, iig. 2, and at ce e, Iig. 4, which embraces the thumb-nutf.

. The thumb-nut f is fitted to; the screw y, whiclris firmly xed in the block 71.

The bar a may be moved backward or forward simply by turning this thumb-nut to the right or left. The block h is iitted between two 'upright sides risingfrom a fiat base, and is held in any required position by the screws or bolts k L, elongated slots in block h.

' These boltsv work in Theslot l-for the bolt k being simplya straight vertical slot, equal in width to the diameter of the bolt, which forms a movable pivot, on which the block h works when the point c is elevated or depressed.

The slot an for the bolt lo' is simply large enough to A. accommodate the diierent positions ofthe block h.

By this arrangement I can raise or lower the block lt in a vertical direction, and also elcvate'or depress' the center-c, so as to linc correctly with any desired angle to a horizontal line.

The nprights 'i c" being cast in one piece with the base n, asshown in iig. 3, the whole may be attached vreadily to a milling or other machine.

' My invention is operated as follows:

The vbase being firmly secured to the tableof thc machine, raise, lower, or incline the block h. until the center c will exactly till the counter-sink in the lend of the arbor or other work supported. Screw unthc bolts lo la', and the block h is held lirmly in its position. The thumb-nutf is then screwed up, so as to bring thecentcrc in close contact with the counter-Sink in the arbor, and the work is ready.` j t Machines of this kind have been made giving an in- Aclined position to the bar a, but yhave always been ot too complicated a nature for actual, practical, and daily use.

Having'thus described the nature, construction, and

uses of my invention, on which l wish to secure Leti ters Patent,

I clairn- The combination of .the bar canut and screw g f, slotted block 71., frame gti i, and vbolts L' It', substantial-ly as and for the purpose set forth.

AMOS H. BRAINARD.

Witnesses: y

ALBAN ANDREW, FRANCIS GARDNER. 

